The invention relates to a push-pull microwave oscillator having two transistors, in which a signal with the frequency of the second harmonic (twice the frequency of the fundamental frequency) is taken from a symmetry point of the oscillaor.
Such a circuit is disclosed in DE-AS No. 23 34 570, corresponding to U.S. Pat. No. 3,939,429 (see FIGS. 6 and 7).
When the frequency of such an oscillator must be kept constant accurately, the phase can be compared with and adjusted in known manner with respect to a reference oscillator. As is customary, the reference oscillation has a lower frequency, because it can then be kept constant to a greater extent regardless of external influences, for example fluctuations in the supply voltage or the temperature, and because it can be more easily conveyed over a transmission path. If, however, the microwave oscillations must be compared, their frequencies must be divided. Dividers for high frequencies, for example more than 1.5 GHz are difficult to implement.